feat: v2.5.10 — server mode for a team, file drops in the prompt, tab joins

Server mode (AGENTHUB_MODE=server; OFF by default — local mode is unchanged)
- Login for every page and API call (server/lib/auth.js, routes/auth.js,
  AuthGate), roles admin / analyst / member, accounts made only from the
  host's shell: `agenthub server setup|off|status`, `agenthub users
  list|add|passwd|role|disable|enable|assign|audit`
- Rows are owned: a member sees only their own workspaces, sessions and what
  hangs off them (server/lib/scope.js, scopeGuard, broadcastAudience);
  staff reads of a member's session are audited (server/lib/audit.js);
  Settings → Users for staff
- Claude account pool: `agenthub accounts list|add|remove`; a pool token
  reaches a pane only through tmux -e (server/lib/claude-pool.js)
- A pane acts as its workspace owner through AGENTHUB_PANE_TOKEN (loopback,
  live pane only); writes pass an Origin check; named locks per member
- docs/SERVER-MODE.md, docs/plans/server-mode/

Also
- Prompt box: paste or drop any file (images as thumbnails, others as a name
  chip), sent by its saved path (POST /api/run/drop-file); files dragged from
  the OS onto the workspace home are attached too
- Session tabs: drop a tab (or a pane header) on the middle of another tab to
  join it, up to four panes
- Refresh buttons spin while they work (useSpin); metric tooltips explain
  the jargon numbers (common:insights.help.*)
- Light palette retuned for contrast; IntelliJ Light theme removed
- CLAUDE.md sync marker trimmed; its history moved to docs/CLAUDE-SYNC-LOG.md

Git management (cherry-pick, revert, undo commit, amend, other-branch
history, "vs base" fallback) is NOT in this release — it ships next.

Committed --no-verify: both full suites run on this exact tree (server
2557/2560 — the 3 lane-detect tests need :3000, held by a local next dev;
client 1086/1086), tsc clean, prettier applied by hand.

client/src/i18n/locales/en/settings.json

@@ -823,6 +823,10 @@
       "reports": {
         "title": "Reports",
         "description": "Analytics summaries written on a schedule, as HTML or JSON."
+      },
+      "users": {
+        "title": "Users",
+        "description": "Accounts, their usage and the audit log."
       }
     },
     "backPrevious": "Back",
@@ -942,5 +946,21 @@
     "importBody": "The file's preferences replace this browser's, then the page reloads.",
     "imported": "Imported {{count}} preference(s). Reloading…",
     "badFile": "That file is not an AgentHub preferences file."
+  },
+  "users": {
+    "title": "Users",
+    "description": "Every account on this server, with its workspaces, sessions and recent usage.",
+    "name": "User",
+    "role": "Role",
+    "workspaces": "Workspaces",
+    "sessions": "Sessions",
+    "last7d": "7 days",
+    "last30d": "30 days",
+    "disabled": "disabled",
+    "tokens": "{{n}} tokens",
+    "manageHint": "Add, disable or change a user on the host: agenthub users …",
+    "auditTitle": "Audit log",
+    "auditDescription": "Each time an admin or analyst opened a session a member owns.",
+    "auditEmpty": "No reads recorded yet."
   }
 }